Groundwater use for crops may reduce vital water supplies for streams
Researchers have found that groundwater pumping used to irrigate cannabis crops in Northern California may have significant impacts on nearby streams and aquatic ecosystems.
The study was conducted by scientists from Simon Fraser University, the University of California, Berkeley, and the United States Department of Agriculture. Their findings were published in the Journal of Hydrology and focused on watersheds in California's Emerald Triangle, one of the world's most recognized cannabis-growing regions.
The researchers examined how water pumped from underground sources affects streamflow in mountain headwaters. These streams are important because they provide habitat for fish, including salmon, and supply water to larger river systems downstream.
"People often think of groundwater or aquifers as a separate resource from streams. But in many landscapes, they're connected parts of the same system," said Jesse Hahm, assistant professor of geography and co-author of the study.
Using an advanced modeling approach, the team evaluated 580 different scenarios. The analysis showed that groundwater pumping during the growing season can reduce streamflow, especially during summer when rainfall is limited and irrigation demand is high.
Under realistic farming conditions, some seasonal streams stopped flowing up to five weeks earlier than normal. In certain situations, streams that typically flow throughout the year dried up completely during summer months.
The impacts were most severe during dry years and in areas with limited groundwater storage. Researchers also found that even a relatively small amount of cultivated land could influence streamflow when groundwater extraction occurs in sensitive locations.
Scientists explained that groundwater and streams are often closely connected. When water is pumped from underground, it can reduce the amount of water available to nearby streams, although the effects may not be immediately visible.
The study highlights growing concerns about water management across western North America. Warmer temperatures and reduced snowpack are changing how water is stored and released into the landscape, increasing pressure on groundwater resources.
Researchers say understanding these relationships can help decision-makers balance agricultural production with environmental protection. Improved water planning may help support farm operations while protecting fish habitat and maintaining healthy stream ecosystems in a changing climate.
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